Rocket powder



June 17, 1952 J J, JR- 2,600,678

ROCKET POWDER Filed March 11, 1949 INVENTOR JOHN J. O'NEILL, JR.

7w Maw ATTORNEYS.

Patented June 17, 1952 UNITED" s'rers ROCKET POWDER Delaware Application March 11, 1949, Serial N 0. 80,959

1 Claim.

This invention relates generally to giant powder grains, such as are used for the propellent fuel in rockets, and for energizing gas pressure systems for the actuation of apparatus of various types.

Giant powder grains for use as the fuel in rockets are generally in the form of cylinders, having a diameter on the order of l to 12 inches and a length on the order of about 1 foot or more. It is customary to provide the exterior of such a giant powder grain with an inhibiting sheath, whereby to preclude the possibility of ignition at the exterior cylindrical. surface, and thus to compel the combustion of the powder grain to proceed from one end toward the other.

Heretofore the efiorts. of those working in the art have been addressed toward. the objective that the rate of gas production at any increment of time during the combustion of the grain be uniform, and to increase the burning surface it has been proposed to provide the grain with axially extending channels, and to insert therein cores of propellent powder; When. ignition takes place at one end of the grain, it proceeds not only from end to end, but radially outward from the channel and radially inward from the exterior of the core. The increasing circumference of the burning area about the channel is substantially balanced by the decreasing circumference of the burning area of the core, so that the rate of gas production becomes substantially uniform.

The object of the present invention is to provide such a giant powder grain wherein the rate of gas production varies accordance with desiderata, so as to produce progressive, retrogressive or intermittent burning.

Othe r objects will become apparent to those skilled in the art when the following discussion is read in connection with the accompanying drawings, in which:

Figure 1 is a longitudinal sectional view of a giant powder grain constructed in accordance with one embodiment of the present invention, wherein a progressively increasing burning rate is achieved from end to end;

Figure 2 is a longitudinal sectional view of a giant powder grain constructed in accordance with another embodiment of the invention, wherein the burning rate of the successive increments decreases from end .to-end and Figure 3 is a longitudinal sectional view of a giant powder grain constructed in accordance with a third embodiment of the invention, wherein the burning and consequently the gas production of the grai is intermittent.

In general, the present inventioncontemplates the construction of a giant powder grain having a series of successively ignitable explosive charges. In the case of the usual cylindrical grain wherein the exterior surface is provided with an inhibitor sheath and one of the end surfaces is exposed for ignition, the several eX-- plosive charges are arranged in strata lying substantially parallel with the end surface, which is exposed for ignition. The several explosive charges may be suitably condensed within a mold Or within the inhibitor sheath, as disclosed, for example, in United States Patent Number 2,417,090, granted March 11, 1947, to C. E. Silk et 2.1., or in the copending application of myself and C. E. Silk, Serial Number 76,842, filed February 16, 1949, it being understood that the aforesaid prior patent and application contem plate a continuous, as distinguished from a stratified, explosive charge, however.

Where it is desired that the rate of gas evolution of the giant powder grain increase as combustion proceeds from end to end thereof, the several explosive charges of the stratified series maybe either chemically Or physically adjusted to control their volumetric burning rates in accordancewith the conditions of operation desired. In its simplest form, to produce a progressive burning giant grain, the invention contemplates the arrangement of a stratum of slow burning propellent powder adjacent the ignition end of the giant grain, and therebeneath (so as not to be ignited until the first stratum is substantially consumed) is arranged a stratum of faster burning propellent powder. In order to further increase the progressiveness of the rate of burning, a third stratum may be inserted beneath the second stratum aforesaid. Such a third stratum may be of propellant powder having a still higher burning rate, or it may be arranged so as to expose a greater surface for combustion, as for example, by the provision of axial channels. Similarly, to produce a giant rain whose burning rate is retrogressive, the several strata. are arranged. in reverse order (it being understood that any stratum whos surface increases as composition proceeds will have an individual burning rate which progressively increases).

When it is desired that the gas evolution from such a giant powder grain be intermittent, the several explosive charges of the series (which may be all of the same burning rate or of difierent burning rates) are separated by suitable slow burning material, which is ignitable by the combustion heat of the stratum ahead of it, and which is capable of igniting the stratum behind it after a predetermined hiatus.

Referring now to Figure 1 of the drawings, the giant powder grain comprises a series of explosive charges I, 2, 3, and 4, arranged in strata, one above the other, so that the interfaces are substantially parallel to the upper end 5 of the assembly. The exterior surface of the grain is encased by an inhibitor sheath 6 of a character well known in the art, which prevents ignition of the several explosive charges at their peripheries. The lower end of the grain may also be covered by a disk 1 of suitable inhibiting material. In the embodiment shown, the explosive charge I, may consist of a relatively slow burning propellent powder, such as one compounded according to the following formula:

Composition A Per cent Nitrocellulose (12.6% nitrogen) 61 Nitroglycerine 19 Triacetin 9 Centralites 11 The foregoing Composition A has a lineal burning rate, at a pressure of a thousand pounds per square inch, of approximately 0.2 inch per second. Beneath the charge I, the next charge 2 of the series is inserted. The charge 2 in this embodiment has a faster burning rate than the charge I, and may, for example, be composed according to the following formula:

Composition B Per cent Nitrocellulose (12.6% nitrogen) 50 Nitroglycerine 43 Centralites 7 Such a composition has a lineal burning rate, at a pressure of a thousand pounds per square inch, of approximately 0.4 inch per second, and is consequently faster than that of Composition A.

Beneath charge 2 there is inserted a charge 3 of still faster burning propellent powder, which may, for example, be composed according to the following formula:

Composition 0 Per cent Nitrocellulose (12.6% nitrogen) 42 Nitroglycerine 42 Trinitrotoluene Centralites 6 Such composition C has a lineal burning rate, under a pressure of a thousand pounds per square inch, of approximately 0.6 inch per second.

Each of the explosive charges I, 2 and 3 is arranged so that combustion proceeds axially through the respective strata, and consequently the surface area exposed for combustion remains substantially constant during the burning of the respective strata. In contrast therewith, the explosive charge 4, which is disposed beneath charge 3 and may be of the same chemical composition as charge 3, is provided with an axial channel 8 so that combustion of charge 4 proceeds not only axially from its upper end surface toward its lower end surface, but also radially outward from channel 8, with progressively increasing burning area. Thus, while charge 4 may be of the same composition as charge 3, the increase in burning area results in a greater volumetric burning rate for the charge 4, and the burning rate progressively increase as combustion proceeds, because the burning area is progressively increasing.

When it is desired that the giant powder grain be retrogressive, i. e., one in which the burning rate decreases from beginning to end of its combustion period, the order of arrangement of the several charges I, 2, 3, and 4 may be reversed, or in other words the inhibiting disk I may be placed upon the upper end of the grain, and the lower end thereof exposed for initial combustion. In that event, charge 4 will nonetheless have a burning rate which, per se, is progressive.

In Figure 2 there is disclosed a further embodiment, wherein the giant grain is designed to have a very high rate of gas evolution upon initial ignition, followed by a reasonably high rate for a substantial time period, then followed by a period of delay in which the gas evolution is substantially nil, and finally by a period in which the rate of gas evolution again becomes substantial, being less than in the initial periods. Such a grain is adapted for use in controlling the trajectory of a rocket, as for example, in situations where it may be desired to project the rocket vertically during the initial periods, then to provide an hiatus during which time there is no substantial jet propulsion, so that the trajectory may flatten out, whereupon the additional charge comes into play to project the rocket horizontally.

In the form shown in Figure 2, the giant grain has an external inhibiting sheath 6, and, an inhibiting end member I, as in the previous embodiment. Within the sheath 6 is arrangeda series of explosive charges II, I2, and I3. The charge I I may be a very fast burning propellant, such as Composition C above, and this stratum consists of a core I8 within an annulus I9, so that combustion proceeds not only axially but radially from the interspace. Between the charges I I and I2 there is interposed a disk I4, which may be of sufliciently slow burning or incombustible material to delay ignition of stratum I2 until stratum I I is consumed, or nearly so. Polystyrene is suitable for disk I4. If the disk I4 fits tightly Within the sheath 6, a succession of suitable vents I5 are arranged about its outer edge, and the vents I5 may, if desired, be charged with a hot burning material to assure the transmission of ignition from stratum II to stratum I2 after stratum II has been substantially consumed. At the end of channel I8, however, disk I4 is imperforate, so as to preclude the ignition of stratum I2 until stratum II is substantially consumed.

Stratum I2 may be composed of propellent powder of the same composition as that in stratum II. Thus, while the lineal burning rate of charges II and I2 are the same, the volumetric burning rate of the latter is less than that of the former, because the latter is not provided with axially extending channels, and consequently combustion can only proceed from end to end thereof.

Beneath charge I2, a disk It of suitable incombustible or very slow burning material, such as polystyrene, is interposed. The disk It is provided with a vent H, which may be charged with a column of delay composition. The delay composition may be any material capable of sustaining its own composition after ignition by charge I 2, and capable of igniting charge I3, such as one of the compositions usually employed in delay trains or one of the propellants. Preferably the material contained within the vent I1 is a gasless or substantially gasless exothermic reacting composition, such, for example, as:

Composition D Parts Barium peroxide 75 r Selenium Talc Composition E Parts Powdered lead 72.4 1 Powdered selenium 27.6

Both Composition D and Composition E are such that an exothermic reaction is initiated by exposure to adjacent combustion of propellent 1 powder, which reaction proceeds progressively without the production of gas, and is capable of igniting an adjacent increment of propellent powder. The width (1. e., the axial dimension) of the disk 16 depends upon the time hiatus which is desired between the burning of charge i2 and the ignition of charge I3. The greater the length of the column of a given material within vent H, the longer the hiatus between the coinpletion of burning of charge l2 and the ignition of charge I3.

Beneath the disk 16, and arranged to be ignited by the material in vent I1, is the final explosive charge of the series. The latter may be composed of propellent powder of any chosen burning rate, as for example, either of Composition A, B, or C.

In Figure 3, a further embodiment is illustrated, in which the gas evolution, as combustion of the "giant grain proceeds from end to end, is intermittent, or pulsating. In this case a series of explosive charges 2!, all of the same composition (either fast or slow burning) are arranged within an inhibiting sheath 6. The several charges 2| are separated one from the other by layers of slow burning material 22, which may be either of Composition D or E above, or any other suitable delay material capable of being ignited by the charge above and sustaining its own combustion (or exothermic reaction) and ultimately igniting the charge below it. As in the previous embodiment, the axial dimension of the several layers 22 is determined in accordance with the time period of delay desired between completion of combustion of the stratum above it, and ignition of the stratum below it. Accordingly, when the giant grain of Figure 3 is ignited at its upper end, gas is evolved by the first charge 2!, which burns from the exposed end axially until the delay layer 22 is encountered. Thereupon the evolution of gas substantially ceases, while'the ignition is proceeding through layer 22. Evolution of gas in substantial proportions does not begin again until after the layer 22 has ignited the next succeeding explosive charge 2|, etc.

In the manufacture of giant grains in accordance with the present invention, the individual explosive charges may be successively compressed. cast or molded within the sheath from the sheath 6: when combustion of the stratum therebehind has developed sufficient pressure to'ldislodge or disrupt the separator. In such cases it is desirable to provide the combustion chamber with a suitable device for trapping theseparator, or the fragments thereof.

From the foregoing description those skilled in the art should readily understand that the inventionaccomplishes its objects, and provides a giant powder grain having a variable and controllable rate of gas evolution, the several elements of which may be adjusted either physically or chemically, or both, to fit the needs of the problem at hand.

While three specific embodiments of the invention have been disclosed in full, it is to be distinctly understood that the invention is not limited to the .details of said embodiments'but that the principles of the invention are susceptible of diversvariations and adaptations without departing from the spirit of the invention, or the scope of the appended claim.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

In a giant powder grain having an ignition surface at the end and a series of explosive charges arranged in strata substantially parallel with said end surface, the combination of separators between said strata, said separators consisting essentially of substantially gasless slow burning material.

.JOHN J. O'NEILL, Ja.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 778,788 Maxim Dec. 27, 1904 1,018,312 Gherassimoff Feb. 20, 1912 1,074,809 Newton Oct. 7, 1913 2,114,214 Damblanc Apr. 12, 1938 FOREIGN PATENTS Number Country Date 27,197 Great Britain 1890 26,430 Great Britain 1907 566,063 Great Britain Dec. 12, 1944 OTHER REFERENCES Ser. No. 159,143, Zwerina (A, P. 0.), published June 8, 1943. 

